Blood products used for transfusion and transfer of blood components must be routinely screened for the presence of infectious agents such as human immunodeficiency virus (HIV), hepatitis viruses, human T-lymphocytotropic virus, and cytomegalovirus. Such agents typically are detected by either identification of viral antigens or by detection of an immune response to the virus (i.e., host-derived anti-viral antibodies) using enzyme immunoassay analysis (EIA) or radioimmunoassays (RIA). Immunoassay techniques are limited in their ability to detect the presence of viral contaminants in early stages of infection, with the window period between infection with a virus and detection by immunoassay techniques varying from two to four weeks for HIV and up to about 10 weeks for hepatitis C virus (HCV). Techniques such as reverse-transcriptase polymerase chain reaction (RT-PCR) or branched chain DNA analysis can shorten the time period between infection and detection, but are cost prohibitive for use on an individual donor basis and do not eliminate the window period.